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A063543 a(n) = n - product of the nonzero digits of n.

%I A063543 #56 Dec 08 2024 23:51:37
%S A063543 0,0,0,0,0,0,0,0,0,9,10,10,10,10,10,10,10,10,10,18,19,18,17,16,15,14,
%T A063543 13,12,11,27,28,26,24,22,20,18,16,14,12,36,37,34,31,28,25,22,19,16,13,
%U A063543 45,46,42,38,34,30,26,22,18,14,54,55,50,45,40,35,30,25,20,15,63,64,58
%N A063543 a(n) = n - product of the nonzero digits of n.
%C A063543 The graph somewhat resembles wisteria flowers.
%H A063543 Harry J. Smith, <a href="/A063543/b063543.txt">Table of n, a(n) for n = 1..2000</a>
%H A063543 N. J. A. Sloane and Brady Haran, <a href="https://www.youtube.com/watch?v=o8c4uYnnNnc">Amazing Graphs II (including Star Wars)</a>, Numberphile video (2019).
%F A063543 a(n) = n - A051801(n).
%e A063543 a(20) = 20 - 2 = 18.
%p A063543 a:= n-> n-mul(i, i=subs(0=1, convert(n, base, 10))):
%p A063543 seq(a(n), n=1..80);  # _Alois P. Heinz_, Aug 18 2019
%t A063543 Table[n - Times@@DeleteCases[IntegerDigits[n], 0], {n, 70}] (* _Alonso del Arte_, Dec 15 2013 *)
%o A063543 (PARI) a(n) = my(d=select(x->(x!=0), digits(n))); n - vecprod(d); \\ _Michel Marcus_, Jan 13 2020
%o A063543 (Python)
%o A063543 def a(n):
%o A063543     digits = map(int, str(n))
%o A063543     product = 1
%o A063543     for d in digits:
%o A063543         if d != 0:
%o A063543             product *= d
%o A063543     return n - product
%o A063543 [a(n) for n in range(20)]
%o A063543 # _Elisabeth Zemack_, Sep 16 2019; corrected by _Fabio Somenzi_, Jan 13 2020
%o A063543 (Magma) [n - &*[a: k in [1..#Intseq(n)] | a ne 0 where a is Intseq(n)[k]]: n in [1..100]]; // _Marius A. Burtea_, Sep 16 2019
%Y A063543 Cf. A051801, A063114.
%K A063543 nonn,base,easy,look
%O A063543 1,10
%A A063543 _N. J. A. Sloane_, Aug 14 2001
%E A063543 More terms from Larry Reeves (larryr(AT)acm.org), Aug 14 2001